We present a minimal but crucial microscopic theory for epitaxial graphene and graphene nanoribbons on the 4H-SiC(0001) surface - prototypical materials to explore physical properties of graphene in a large scale. Coarse-grained model Hamiltonians are constructed based on the atomic and electronic structures of the systems from first-principles calculations. From the theory, we unambiguously uncover origins of several intriguing experimental observations such as broken-symmetry states around the Dirac points and new energy bands arising throughout the Brillouin zone, thereby establishing the role of substrates in modifying electronic properties of graphene. We also predict that armchair graphene nanoribbons on the surface have a single energy gap of 0.2 eV when their widths are over 15 nm, in sharp contrast to their usual family behavior.
Bibliographical noteFunding Information:
S.K. was supported by KIST internal project (Grant no. 2E23590 ). J.I. acknowledges the support of the NRF of Korea through MEST Grant no. 2006-0093853 and the 2010 Korea-Sweden research cooperation program. H.J.C. was supported by the NRF of Korea (Grant nos. 2009-0081204 and 2011-0018306 ). Y.-W.S. was supported by QMMRC No. R11-2008-053-01002-0 and Nano R&D program 2008-03670 of the NRF of Korea. Computational resources have been provided by KISTI supercomputing center (Project no. KSC-2011-C3-05 ) and the KIAS CAC.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Materials Chemistry